Rapid development of digital communication system brings about higher requirements on reliability of data communication, however, in a bad channel environment, especially in a high data rate or high-speed movement environment, multi-path interference, Doppler frequency shift and the like will severely affect the system performance. Therefore, effective error control technique, especially HARQ (Hybrid Automatic Repeat reQuest) technique becomes a hot point of the research made on communication field.
In HARQ mode, the codes transmitted by a transmitting end are not only able to detect errors, but also have a certain error-correcting capability. After receiving codes, a decoder at the receiving end firstly detects errors: if the errors are within the error-correcting capability of the codes, then the errors are corrected automatically; if there are too many errors that they go beyond the error-correcting capability of the codes, but the errors can be detected, then the receiving end transmits a decision signal to the transmitting end via a feedback channel to ask the transmitting end to re-transmit the information.
In an OFDM (Orthogonal Frequency Division Multiplexing) system, an ACK/NACK (Acknowledged/Non-Acknowledged) control signaling is used to indicate whether the transmitted information is correct or erroneous, thereby determining whether the information needs to be re-transmitted or not.
At present, it is specified in LTE (Long Term Evolution) system that an ACK/NACK message related to uplink data is transmitted in PHICH. One ACK/NACK message corresponds to one PHICH.
One ACK/NACK message corresponds to 1-bit original information, and then the 1-bit original information is encoded repeatedly for three times and then is k-times spectrum spread, becoming m bits, wherein m=3×k; after BPSK (Binary Phase Shift Keying) modulation, m bits are respectively mapped to 3 resource groups, each of which includes 4 physical sub-carriers. When the cyclic prefix is a normal cyclic prefix, k=4; when the cyclic prefix is an extended cyclic prefix, k=2, in which case, two PHICHs can be mapped to three same resource groups for frequency division multiplexing. Meanwhile, two PHICHs can be multiplexed on the same physical sub-carrier via I path and Q path.
Generally, as for normal cyclic prefix and extended cyclic prefix, allocation of PHICH resources should be performed by dividing a plurality of PHICHs into several groups according to its spectrum spreading multiple k and the specification on the number of physical sub-carriers included in each resource group, and each group of PHICHs includes a plurality of orthogonal codes according to the corresponding two positions of orthogonal I path and Q path and the specification on spectrum spreading multiple.
Therefore, a mapping relationship between a PHICH and PHICH group, orthogonal codes and I/Q path has to be determined for both normal cyclic prefix and extended cyclic prefix so as to facilitate allocation of PHICH resources. This enables the HARQ function to be achieved in a practical system, but meanwhile requires assurance of minimum interference between users and high utilization of system resources to improve performance of the system. However, there is no preferable solution currently for solving the above problem.